From the (1) University Department of Obstetrics and Gynaecology, (2) Department of Primary Care and Population Sciences, (3) Haemophilia Centre and Haemostasis Unit, The Royal Free Hospital, London, UK

Summary

To assess variations of coagulation factors in women, 123 women
were included in a cross-sectional study of the effect of age, ethnic
origin, blood group and menstrual cycle on surface induced coagulatßion
time (activated partial thromboplastin time) and plasma levels of
Factor VIII clotting assay, von Willebrand factor antigen, von Willebrand
factor activity and factor XI. The effect of menstrual cycle was
further assessed in a longitudinal study including 39 Caucasian women,
20 of whom were using combined oral contraceptives. Activated partial
thromboplastin time was longer in women with blood groups B
or O, and plasma levels of factor VIII clotting assay, von Willebrand
factor antigen and von Willebrand factor activity were significantly
higher in black women. Fibrinogen, von Willebrand factor antigen and
von Willebrand factor activity concentrations showed strong cyclic
variations with peak values in the luteal phase. This pattern was
dampened for von Willebrand factor antigen and von Willebrand factor
activity but completely disappeared for fibrinogen with the use of combined
oral contraceptives. There was a cyclical pattern for factor VIII
clotting assay in pill users, evidence of which was not evident in non-pill
users. There were strong associations between the levels of von
Willebrand factor antigen and von Willebrand factor activity and age,
with levels rising by an average of 0.17 and 0.15 U/ml, respectively, for
each 10 year increase in age. In conclusion, there are great inter- and
intraindividual variations in coagulation markers in women due to
different physiological conditions such as age, ethnicity, blood group
and phases of the menstrual cycle. However, there were no significant
associations between coagulation markers and weight, alcohol consumption
or smoking status.